Dicinnamates

Photodimerization of cinnamic acids and its derivatives generally proceeds with high efficiency in the crystal (176), but very inefficiently in fluid phases (177). This low efficiency in the latter phases is apparently due to the rapid deactivation of excited monomers in such phases. However, in systems in which pairs of molecules are constrained so that potentially reactive double bonds are close to one another, the reaction may proceed in reasonable yield even in fluid and disordered states. The major practical application has been for production of photoresists, that is, insoluble photoformed polymers used for image-transfer systems (printed circuits, lithography, etc.) (178). Another application, of more interest here, is the use that has been made of mono- and dicinnamates for asymmetric synthesis (179), in studies of molecular association (180), and in the mapping of the geometry of complex molecules in fluid phases (181). In all of these it is tacitly assumed that there is quasi-topochemical control in other words, that the stereochemistry of the cyclobutane dimer is related to the prereaction geometry of the monomers in the same way as for the solid-state processes. 

The bis(4-dimethylaminocinnamate) derivative of 8,9,10,1 l-tetrahydrodibenz[a,/j]acridine-10,11 -diol 5 was used to determine the absolute configuration at C-10 and C-ll. A clear negative dicinnamate exciton Cotton effect, free from interactions with the aromatic residue of the molecule, was observed at the long-wavelength part of the spectrum162. 

EDTA in water. Ru(bpy)2 + and its dicinnamate were immobilized in a membrane prepared from cinnamate of poly(vinyl alcohol) by photocrosslinking 51), and the immobilized complex sensitized the photoreduction of MV2 +. ... 

For an early example of photochemical asymmetric synthesis in irradiation of L-erythritol 1,4-dicinnamate derivatives see B. S. Green, A. T. Hagler, Y. Rabinsohn and M. RejtO, Isr. J. Chem., 916ITI, 15, 124. 

Dimerization.—A detailed study of the effect of methoxy-substitution on intramolecular cyclization of the dicinnamates (86) has been reported.From the results it is clear that the m-methoxy-derivatives photocyclize much more rapidly than the other derivatives. In a quantitative investigation where the m-methoxy-derivative (86b) was compared with the parent compound (86a), the authors established that with n = 2 or 3 the major cyclization mode (>91%) led to the -truxinate compound (87), whilst with n = 4 the parent compound (86a) gave the 8-truxinate (88) and the -truxinate (87) in a ratio of 1 3... 

A mechanistic study of the (2+2)-cycloaddition reaction of the dicinnamates (175) has been reported. ... 

A study with the ethyl ester showed that photopolymerization took place in the crystalline state but not in the melt 26>. A further example of this type of polymerization is reported for polymethylene dicinna-mates, typical of which are tetramethylene dicinnamate and ethylene dicinnamate 27>. 

The diastereoselection of the intramolecular photocycloaddition of 1,4-erythritol dicinnamates (161b) has been explained by diastereoisomeric transition states involving different steric constraints and on the basis of a simulation of the diastereomeric ground-state conformations believed to lead to the observed adducts. Modification of the chiral auxiliary in 161c led to disappointing selectivities and the chemical yields in the desired 5-truxinate remained low. 

A detailed survey of this figure reveals that the nickel sulfate heated at temperatures above 450° has a number of acid sites having acid strength lower than pK = +1.5, but has no or little catalytic activity. The acidity of acid strength higher than pK = — 3.0 best correlates with the catalytic activity for the depolymerization reaction. This is further confirmed by the fact that nickel sulfate and cupric sulfate lost entirely their catalytic activity when the acid sites whose acid strength is equal to or lower than pK = — 3 were poisoned with dicinnamal-acetone, a basic indicator of pK = — 3 12). 

Nagata and Hizakae [153] reported preparation of a series of photocross-linkable biodegradable polymers by condensation of dichlorides of 4,4 -(adipoyldioxy)dicinnamic acid and alkane diols of various methylene lengths. They also used various poly(ethylene glycols) with molecular weights ranging from 200 to 8,300. 

Ring and open-chain derivatives of L-erythritol 1,4-dicinnamate have been irradiated yielding products of photochemical asymmetric synthesis, in which intramolecular 2-1-2 cycloaddition occurs to give L-erythritol esters of cyclobutane-1,2-dicarboxylic acid the 2,3-di-O-methyl derivative of l-erythritol gave a high degree of asymmetric induction, whereas the 2,3-0-isopropylidene derivative was much less stereospecific, and gave the opposite cyclobutane enantiomer. ... 

Nagata M, Hizakae S (2003) Synthesis and properties of biodegradable copolymers based on 4,4 -(adipoyldioxy)dicinnamic acid, 1,6-hexanediol, and poly(ethylene glycol)s. J Polym Sci A Polym Chem 41 2930-2938... 

Many macrocyclic compounds have been prepared by the irradiation of oqto-dicinnamates and dicoumaryl derivatives (130, 130-16). > When the tether is a polyglycol unit, the photodimerization is sensitive to alkali metal ions, and crown-ether-Hke structures can be prepared. Intramolecular dimerization reactions can find preparative importance as, for instance, in the preparation of the P- and 8-truxinate dimers from the irradiation of propylene-1,3-dicinnamate and n-butylene-l,4-dicinnamate, respectively. The tether may also function as a chiral auxihary, such as in the irradiation of L-erythritol 1,4-dicinnamate or mannitol hexacinnamate. In the latter case, an excess of the (-l-)-8—truxinate isomer was observed, along with several other isomers. 

Green, B.S., Hagler, A.T., Rabinsohn, Y, and Rejto, M., Photochemical asymmetric synthesis. Irradiation of ring and open-chain derivatives of L-erythritol 1,4-dicinnamate,/sr. /. Chem., 15,124,1977. 

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